1. Field of the Invention
The present invention relates to a noise canceling circuit, a noise canceling method, and a solid-state imaging device.
2. Description of the Related Art
A typical solid-state imaging device (camera), which is mounted on a digital still camera (DSC), a mobile phone, or the like to output digital video, converts an analog signal of a subject image focused through an imaging lens on an image pickup device into a digital video signal using an analog-digital converter (ADC). An image processor incorporated in the camera performs lens shading, defect correction, noise canceling, and the like for the obtained digital video signal, and outputs a final digital video signal.
With recent reduction in pixel size, decrease in a signal-to-noise (S/N) ratio of a video signal outputted from an image pickup device has become noticeable. Deterioration in calculation accuracies of the various types of processing in the image processor due to noise in the video signal outputted from the image pickup device has become an issue. To resolve the issue, another circuit performing noise canceling can be further provided at a first stage in the image processor that performs the various types of typical processing as described above to remove noise in an imaging signal from the image pickup device.
However, the noise canceling circuit typically provided in the image processor uses a two-dimensional filter and thus has a line memory (for example, see Japanese Patent Application Laid-open No. 2006-20050). Accordingly, when the noise canceling circuit is provided at the first stage in the image processor, the circuit scale and the power consumption are increased. If the noise canceling is performed based on a one-dimensional array of pixels without using the line memory, it is difficult to distinguish between noise and a sharp part in which contrast information sharply changes. Therefore, the sharp part is also attenuated by the noise canceling, which provides a reduced sense of resolution and a deteriorated image quality.